Rice growers have tools to stop weevil

A variety of insecticides being tested by LSU AgCenter researchers show promise for helping Louisiana rice growers get rid of their No. 1 insect pest — the rice water weevil.

Five seed treatments are at least as effective as Icon, also called fipronil, which is no longer available in the United States, said Mike Stout, LSU AgCenter entomologist.

“Some of them are likely to be safer on crawfish than pyrethroids,” he said. “The efficacy is definitely there.”

Some of the seed treatments might be limited to drill-seeded rice only, he said.

Granular chemicals show potential also, Stout said. “We have a compound that seems to have pretty good activity on larvae.”

Applications of the granular, called dinotefuran, made 20 days after flooding controlled 80 percent of the rice water weevil larvae population, he said. A release date for the chemical has not been set, he said.

Stout said the U.S. Environmental Protection Agency has extended a Section 18 label for the granular insecticide Etofenprox, manufactured by the Japanese company Mitsui, through 2009. The chemical has not worked well at the LSU AgCenter Rice Research Station in Crowley, La. But it has been effective at research facilities in other states, including Arkansas and Texas, he said.

The Louisiana testing at the Rice Station has been done late in the rice-growing season when weevil infestations are extremely heavy, Stout said. Entomologists at the other research facilities typically face lighter infestations.

Karate, which has a chemical structure similar to that of Etofenprox, doesn't work well in a late-season application either, he said.

“When you plant rice late, you can expect to have weevil populations so heavy they can't be controlled with one application,” he said. He said trials in 2007 will include late and early applications of Etofenprox.

Stout and Dustin Harrell, LSU AgCenter agronomist at the Rice Station, are studying whether lower seeding rates result in greater susceptibility to yield losses from the rice water weevil.

Another project seeks to determine the characteristics of some rice varieties that allow them to better tolerate weevil injury. These projects are being funded by the USA Rice Foundation, leveraged by funding provided through the Louisiana Rice Research Board.

Yet another project funded by the board is aimed at finding out if applications of a plant hormone can stimulate plant resistance to weevils. The idea worked well in the greenhouse, Stout said.

“Next year, we'll try to spray it in the fields,” he said.

Work also continues on stem borers. Stout said he has a greenhouse study of sugarcane borers to find out which rice varieties the pest prefers.